Studies on the genetic basis for thermotolerance inArabidopsis thaliana

QK Botany;S Agriculture (General)

Nurcahyanti, Agustina ; Dominy, Peter

University:University of Glasgow

Department:Institute of Molecular Cell and Systems Biology

关键词: Arabidopsis thaliana, thermotolerance, AtMYB64, heat shock protein;   

Others  :  http://theses.gla.ac.uk/631/1/2009nurcahyantimsc%28r%29.pdf

来源: University of Glasgow

【 摘 要 】

Vast tracts of land are available for arable food production but much of this islocated in hot, arid regions. For crops to thrive in these conditions they will needto show improved drought tolerance and also improved thermotolerance as lowwater availability reduces transpiration resulting in increased leaf temperatures.Identification of traits and genes involved in drought tolerance has been one of themajor areas of plant research over the last decade, but thermotolerance hasreceived little attention. In this study two approaches were used to identify thegenetic basis for improved thermotolerance in the model plant Arabisopsis thaliana.In one set of experiments a gain-of-function heat stress screen (44 oC for 3 hours)was performed on a collection of Activation Tagged lines where individual plantswere engineered to transcriptionally activate random sequences in theArabidopsis genome. Preliminary experiments confirmed prior exposure to 37 oCfor 1-3 hours acclimates Arabidopsis so that it survives better a subsequent heatstress event. A total of ~14,600 lines were screened and three mutants wereisolated; secondary screens confirmed their improved thermotolerance phenotype,but in subsequent generations one of the lines developed a hypersensitivephenotype, another reverted to wild type, whilst the third retained itsthermotolererant phenotype. This loss-of-phenotype through generations wasattributed to gene silencing events which are not uncommon in dominantmutants. Further experiments on these three lines are now required to identify theloci of the disrupted gene(s) in each of these lines.In the other set of experiments transgenic lines carrying a construct designed toconstitutively express a MYB transcription factor were characterized. This MYBhas been shown to confer salinity tolerance in Arabidopsis, and transcriptprofiling using cDNA microarrays had identified several sequences may be underthe control of this MYB. Quantitative PCR (QRT-PCR) demonstrated that compared with wild type MYB expression in the transgenic lines was over 500times greater, and that transcript for a small heat shock protein AtHSP17.6, is 17times more abundant. These transgenic lines were shown to have an improvedthermotolerance. Treatment of wild type plants with 5 x 10-4 M ABA increased theexpression of this MYB seven-fold, suggesting this transcription factor forms partof the ABA-dependent pathway for the activation of abiotic stress responses inArabidopsis.